/**
 * A concrete state for customer shopping
 */
public class Shop extends ShopState {
	public static boolean instanceFlag = false; // true if have 1 instance

	private Shop() {
	}

	public static Shop getInstance() {
		if (!instanceFlag) {
			instanceFlag = true;
			return new Shop();
		}
		return null;
	}

	public void shop() {
		System.out.println("The state is shopping now !");
	}
}